The present invention generally relates to the field of rotational position sensors, and more specifically to a magnetic rotational position sensor for sensing each rotational position of a control shaft about a rotational axis over a definable range of rotation.
Electronic fuel injected engines used in motor vehicles typically embody a microprocessor based control system. Fuel is metered or injector activation time is varied in accordance with various engine parameters including the regulation of air flow into the engine via a rotational position of a throttle diaphragm relative to a closed position of the throttle diaphragm. Typically, a shaft is adjoined to the throttle diaphragm to synchronously rotate the throttle diaphragm as the shaft is rotated between the closed position and a maximal open position of the throttle diaphragm. Rotational position sensors are adjoined to or adjacent the shaft to sense each rotational position of the shaft, i.e. each degree of rotation of the shaft relative to the closed position, thereby the rotational position of the throttle diaphragm relative to the closed position is sensed.
One of the problems associated with prior contact rotational position sensors that incorporate a contact element, e.g. a contact potentiometer, is the wear and tear experienced by the contact element that reduces the useable life of the contact rotational position sensor. One of the problems associated with prior magnetic rotational position sensors is magnetic hysteresis. Magnetic hysteresis causes an offset error signal to be generated whenever a magnet of the sensor is advanced from and returned to a reference position of the magnet, or whenever a magnetizable component of the sensor, e.g. a magnetizable pole piece, is advanced from or toward the magnet of the sensor. Annealing the magnet can minimize, but never eliminate, magnetic hysteresis. What is therefore needed is a novel and unique magnetic rotational position sensor that neither incorporates a contact element nor experiences magnetic hysteresis.